Photosensitive electro-optical calculating machine



`)une 8, 1965 T. l. REss 3,188,474

PHOTOSENSITIVE ELECTRO-OPTICAL CALCULA'IIING MACHINE Original Filed Jan.24, 1956 Two I EIGHT f7 A Z4 3f j D E] L] [g1 El THOMAS I. RESS BY#AWN/m..

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nited States Patent imi 3,188,474 PHTOSENSlTl'l/E ELECTRO-OPTICALCALCULATENG MACHENE Thomas l. Ress, Riverton, NJ., assigner tointernational This invention relates to a counting device, andparticularly to an electro-optical device for operation in a binarysequence. The device disclosed herein is similar in certain respects tothe electro optical counter disclosed in my copending application SerialNo. 557,381, iiled I anuary 4, 1956.

This application is a division of my copending application Serial No.560,938, tiled January 24, 1956, now Patent No. 2,985,763, issued May23, 1961.

In an effort to improve and speed up the process of machine calculation,numerous techniques have been developed employing electronic and evenelectro-optical devices. These electronic calculating devices generallyemploy numerous components. As for the electro-optical calculatingdevices, they consist or" a light generating source whose beamtransmission is logically controlled by deflecting elements beforeoperating certain photoelectric cells. in these electro-opticalarrangements, one photoelectric cell must be employed for each positionof count- `ing and each such position cell must be externally activated.The large number of components and the rigidity of operation resultingfrom these prior electro-optical calculating techniques does not makefor the most efcient type of operation. y

Therefore, it is the principal object of this invention to provide aneiiicient and economical electro-optical calculatin g device.

Another object is to provide such a calculating device in whichlight-responsive elements register a plurality of light pulses in codalform.

Another object is to provide an improved electro-optical counter.

According to this invention, the counter consists of a number ofphotoconductors and electro-luminescent spots all of which areelectrically interconnected in a manner to register digit representinglight pulses. Each counting position comprises a pair of inputphotoconductors that are activated by digit representing light pulses.One of these input photoconductors, upon activation, energizes an outputphosphor spot which records and manifests the value represented by thelight pulse. An electro-optical loop circuit formed by this inputphotoconductor and the output spot stores the value entered into thecounter until the next light pulse arrives, or the counter is reset toZero. The appearance of every second or even light pulse in a countingposition activates the other input photoconductor, which serves toenergize a carry phosphor spot for the purpose of transferring the valuein the lower counting position to a higher counting position. The carryphosphor spot also brings about the de-energization of the outputphosphor spot.

Other objects of the invention will be pointed out in the followingdescription and claim and illustrated in the accompanying drawing, whichdisclose, by way of example, the principle of the invention and the bestmode,

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sassari which has been contemplated, of applying that principle.

The single drawing is a schematic diagram showing an electro-opticalcounter according to the invention.

Generally, the invention consists of electrically and opticallyinterconnected conventional photoconductors and electro-luminescentspots in the form of a binary counter. Such a counter is composed ofbasic electrooptical circuits. For example, the series connection of aphotoconductor element and a phosphor spot permits the spot to beactivated when the photoconductor receives oa light pulse. The seriesoperation or" electro-luminescent and photoconductive material isdescribed in Review of Scientiiic instruments (lune 1953) Vol. 24, No. 6pages 471-472. ln the parallel connection of a photoconductor andphosphor spot, the appearance of a light. pulse on the photoconductorde-energizes or quenches the phosphor spot. Two photoconductors inseries with a phosphor spot permit the spot to be activated only if bothphotoconductors receive light pulses. These interconnected componentsmay be placed in printed circuit fashion on an insulated base of alimited dimension with a thin conductive strip between the components.The preferred arrangement is to print the photoconductors andelectroluminescent spots closely together on both sides of a transparentplate such as glass. The disposition of phosphor material andphotoconductor material on opposite sides of a transparent insulator foroptical coupling purposes is described in Mellon Institute of IndustrialResearch, Quarterly Report No. 3 of the Computer Components Fellowship(First Series) April 1l, 1951 to July 11, 1951, Section VI, OpticalComponents for Digital Computers (pages Vl-9 and VI-lO). A conventionalopaque masking plate may be used where a photoconductor must be shieldedfrom adjacent light sources, that is, where feedback is not required.

The drawing illustrates the electrical and optical connections forming afour position binary counter. The solid lines between the componentsindicate electrical connection, and the` dotted lines represent opticalconnections. The squares represent photoconductors, and the circlesrepresent electro-luminescent phosphor spots.

According to this invention, a suitable source of electrical energy 1lprovides the necessary AC. power, for example, 600 volts, through resetswitch 12, to all input photoconductors and all output phosphor spots.Reset witch 12 may be designed to operate manually or automatically. Cam13, with its associated contacts 13a, serves to connect the energysource 1l to the carry spots in each binary order. The counter isthereby capable of recording light pulses and transferring thisinformation between the binary positions, only when reset switch 12 andcam contacts 13a are closed.

As shown, each of the counting positions has two input photoconductorswhich are subjected to the light pulses to be counted. With regard tothe binary-one position, input photoconductors 14 and 215 are subjectedsimultaneously to input light pulses which may be supplied, for example,by a Lucite tube of Y configuration whose stem portion receives thelight pulses, and whose diverging branch portions are optically coupledto photoconductors 14 and 15, respectively, to communicate the receivedlight pulses thereto. A Lucite tube of this sort is disclosed on p. 471of the previously referred to (June 1953) issue of Review of Scientificinstruments and, also, i

in my copending application Serial No. 557,381, tiled January 4, 1956.Input photoconductor 14 is directly connected to input phosphor spot 16and photoconductor 17, and therefore, conducts current to both thesecomponents When a light pulse impinges on photoconductor 14.Photoconductor 15, on the other hand, conducts current to photoconductor18 for energizing the latter after a light pulse impinges onphotoconductor 15.

Photoconductors and 18 have dilferent light-response times to preventboth photoconductors from being energized simultaneously upon theapplication of the first and` every odd numbered light pulse. By this ismeant that, as shown in FIG. 2, there is some delay between the time alight pulse is incident on both of photo-conductors 14 and 15 and thetime the phosphor spot 16 is activated by the illuminated photoconductor14 to cause light to be incident on photoconductor 18. Therefore, thephotoconductor 18 responds to light at a time later than does thephotoconductor 15. Since the input light pulses impinge on bothinputphotoconductors 14 and 15 simultaneously, both conduct current tooutput spot 16 andphotoconductor 18, respectively. Thereupon, outputspot 16 becomes energized, providing radiant energy for photoconductor18. However, before photoconductor 184 can be fully activated by outputspot 16, photoconductor 15 becomes de-activated as a result of thetermination of the input light pulse. Only when the second and everyeven light pulse is applied willl both photoconductors be activatedsimultaneously.

Since photoconductors 15 and 1d are in series with carry spot 19, it isnecessary that both these photoconductors be activated simultaneously ifcarry spot 19 is to be lighted. It is important that the input lightpulse be of a duration which is sutlcient for input photoconductor 15-to bring series-connected photoconductor 18 into an active State beforephotoconductor 15 is returned to its inactive, state. That is to say, asphotoconductor 18 reaches the point of being activated as a result ofcurrent provided by input photoconductor 15 and light beams transferredby output spot 16, input photoconductor 15 reaches the point ofde-activation. Therefore, carry spot 1.9 is incapable of activationduring the time that the rstl andv every odd numbered light pulse isbeing recordedY in the counter.

Output phosphor spot 16 develops a closed loop with input photoconductor14, through an optical feedback arrangement, duringV the time that inputconductor 14 receives al light pulse. Photoconductor 14 andelectroluminescent spot 16 are assumed to be on opposite sides of aglass plate. After the light pulse has been terminated, the radiantenergy fed back by spot 16 to photoconductor 14, serves to make thisphotoconductor conductive, and the electrical energy whichphotoconductor 14 makes available to output spot 16 generates furtherradi'antfenergy, in this way forming a closed loop. Spot 16 alsomaintains photoconductor 18 activated upon the termination of the firstlight pulse. As in the case of photoconductor 14, photoconductor 18 isassumed to be located on a glass plate opposite spot 16.Photoconductors14, and 18 may be on the same side opposite a larger spot1,6I or onseparate plates opposite spot 16. Output spot15rwillcontinueto operate photoconductors 14 and 18 until output spot 16 is quenched orde-energized by the activation of its parallel connected photoconductor17.

4They counter will now be described in terms of its ability tocountlight pulses that are serially entered into the counter through thebinary one position circuit. As

stated above, the entry of the first digit representing light pulsebrings about the energization of output spot 16, which is thenmaintained in an energized state by the photoconductor 14.

' An explanation of the conjoint operation of photoconductor 14fandphosphor spot 16 is as follows: Ignoring, for the time being, the effectofthe photoconductor 17, the photoconductor 14 and phosphor spot 16 areconnected in series and, therefore, divide between them the A.C. voltagefrom source 11 in proportion to the relative impedance values of theseelements. ln the absence of light incident on photoconductor 14, theimpedance of the photoconductor 14, relative to that phosphor spot 16,is sufciently high to maintain the voltage across the spot below a valueat which the spot will become and remain electro-luminescent. Theimpingement of the rst light pulse on photoconductor 14 reduces theimpedance thereof to the extent of momentarily increasing the voltageacross spot 16 to a point Where the spot becomes electro-luminescent.Thereafter, the light received by photoconductor 14 from spot1,6-maintainslthe impedance of the photoconductor sufficiently reducedthat. the voltage across the spot continues to excite the spot intoelectroluminescence.

The `second input pulse activates input photoconductors 14 and 15. Sincephotoconductor 14l is in. an activated state at this time, as a resultof its feedback arrangement with spot 16, the activation ofphotoconductor 14 has no effect on the circuit at this time. However,the activation of photoconductor 15, at the same time thatphotoconductor 18` is activated by output spot. 16, illuminates carryspot 191. The energization of carry spot 19 then causes photoconductors1'7 and. 2(3.to be activated. Inasmuch as photoconductor 17 receivesradiantenergy from carry spot 19 and electrical energy fromphotoconductor 14, photoconductor 17 is activated to quench output spotl16. Photoconductor Z6 maintains carry spot 192 illuminated until cram 13opens contact 13a.

As an explanation of how spot :t9-becomes `and remains illuminated, .thephotoconductors 15 and `18 in series and the photoconductor 29, inparallel with this series combination, together provide `a netphotoconductive impedance which is in series 'with phosphor spot 1.9,and which is interposedibetween this phosphor spot 19 andthe source 11-of A.C. voltage. Thus the A.C. voltage from source 11v will ,be dividedbetween this net photoconductive impedance and the `spot 19in proportiontothe relative impedance values thereof. The photoconductor` 20initially is dark. So long as light is incident on neitherphotoconductor .115 or ,18, or incident on photoconductor `18 only,

the value of the net photoconductive impedance, relative'.

to that of spot 19, is sufficient to maintain the voltage across thespot below a Ivalue at :which the spot will become electro-luminescent.When however, photoconductor -18 is illuminated from spot 16 land when,at the same time, the second light pulse is incident eon photoconductor15, the net photoconductive impedance is so reduced that the voltageacross .spot 19 rises to a value where the spot ybecomes illuminated.When the spot 19 becomes illuminated, the light therefrom, which isincident on. photoconductor Ztl, reduces the impedance lof this lastnamed photoconductor to maintain .the net photoconductive impedance at`a value where the voltage developed` across spot 19 continues to exciteit into electro-lumines, cence even after `both of photoconductorsy'15'rand 18 have lreturned to the dark state.

The quenching action of the photoconductor 1'7- is as follows. Aspreviously explained, the series combination of photoconductor |14 `andphosphor .spot 16 provides a voltage dividing effect which, whenphotoconductor 14 receives light from spot `16, serves to maintain thevoltage across `spot 16 at a value which continues to excite the spotinto electro-luminescence. This previous explanation assumes that thephotoconductor 117 is dark, and that the series combination `of elements14 and 16 operates as previously described, despite the fact that,ibeoause photoconduct-or 17 is in parallel with spot 16, the combineddark impedance of photoconductor 17 andimpedance of spot 16 is a neteffective impedancewhich is -in series with photoconductor i141, andiwhich is somewhat less than the impedance which would be -in serieswith this photoconductor if yonly the spot 16 ,were present.

Consider now what happens when photoconductor 1'7 receives light fromphosphor spot 19. The ensuing re-` duction in impedance ofphotoconductor 17 reduces the combined impedance (of photoconductor .17and spot 16) to a point where, due to the voltage dividing actionprovided by `this combined impedance and the impedance of photoconductor114 when illuminated, the voltage across spot 16 no longer is able to`sustain the spot 16 in illuminated condi-tion. Under thesecircumstances the light output from spot `16 terminates to thereby causethe impedance of photoconductor 14 to -rise to its dark impedance value.As previously explained photoconductor 14, when at its dark impedancevalue, prevents spot |16 from becoming illuminated.

At the same time that carry spot 19 activates quenching photoconductor117 for the purpose of tie-energizing output spot .16, carry spot 19causes output spot 23 in the binary two position to be illuminated inthe following manner. The illumination of car-ry spot .19 brings about atransfer of radiant energy to the binary two position input conductorsZ1 .and 22. The activation of photoconductor 21 develops a current whichilluminates -output spot 23. Soon after this spot is energized, itlfeeds back radiant energy to photoconductor 21, thereby developing .aclosed loop dor storing a digit 2.

Photoconductor 22 is also activated by the radiant energy made availableby carry spot 19. Before photoconductor 24 can be simultaneouslyactivated by the radiant energy provided by output spot 23,photoconductor 22 is caused to be tie-activated. This is accomplished bythe de-energization of carry spot 419 as a result of the opening of camcontacts 13a. The momentary cle-energization of carry spot 19 terminatesthe loop circuit formed by carry `spot 19 and photoconductor 20. Sinceradiant energy is not available for the short interval in which contacts113:1 are open, photoconductor 20 is de-activated and unable to developcurrent for spot 19. The subsequent closure of cam -contacts 13a cannotre-energize this loop circuit, since photoconductor 2t) can only beactivated by the simultaneous application of radiant and electricalenergy. It should be clear that the operation of cam 13 must besynchronized with the input light pulses.

At the time that the third light pulse is entered into the binary onecircuit, all the elements in the binary one circuit lare in .arie-activated state. The cle-activated condition of -output spot 16indicates an absence of a digit 1 value in the counter. Carry spot 19 isalso de-activated lat this time, as explained above. Only inputphotoconductors Z1 and Z4 and output spot 23 in the binary two circuitare in an activated state. Output spot 23 continues to maintain inputphotoconductor 211 `and output photoconductor 24 in an activated state.

The appearance of a third light pulse in the binary one circuitactivates photoconductors 14 and 15. The effect of this light pulse onthe binary one circuit is similar to that in which the first light pulsehad been entered. That is to say, output spot 16 is energized, forming aloop circuit with photoconductcr 14. `Carry spot 19 cannot be energizedat this time. Therefore, at the end of .the third iight pulse, outputspots 16 .and l23 are illuminated to indicate the absence of a digit 3.The opening of cam contacts `13a at the end of the third input pulse hasno effect on the counter since carry spot `19 and all the other carryspots are in a tie-energized state.

The input of a fourth light pulse to the binary one circuit has aneffect on this circuit identical to that 'already explained in the caseof the second light pulse.

`That is to say, photoconductors and 18 are simultaneously activated toenergize -carry spot 19, whose radiant energy activates photoconductor17 and brings about fthe -de-energization of output spot 16. The radiantenergy transferred from carry spot 19 to photocouductor 21 has no effecton the binary two circuit inasmuch as photoconductor 21 is already in anactive state. However, the transfer of radiant energy from carry spot 19to photoconductor 22 places photoconductors 22 and 24 simultaneously inan activated condition. The electrical energy which is now transferredfrom photoconductor Z4 to carry spot 25 puts this carry spot in anilluminated state. Carry spot 25 then transfers radiant energy tophotoconductors 26, 27, 28 and 29. The activation of photoconductor 26develops a loop circuit with carry spot 25 for the purpose of keepingcarry spot 15 energized until cam contacts 13a are opened. Theactivation of photoconductor 27, which is parallel to output spot 23,causes photoconductor 27 to quench output spot 23.

The activation of photoconductor 28, on the other hand, by the radiantenergy transferred from carry spot 25, causes output spot .3u of thebinary four circuit to be illuminated, developing a loop circuit betweenphotoconductor 28 and output spot 30. The transfer of radiant energyfrom carry spot 25 to photoconductor 29 has no effect on the binary fourcircuit, as previously explained with regard to the binary one and twocircuits. After the entry of the fourth input light pulse, when camcontacts 13a are opened, output spot 3u alone is illuminated to indicatea digit 4 inthe counter.

The entry of subsequent light pulses in a counting sequence will in asimilar fashion operate the electrooptical counter. That is to say, theentry of a fifth pulse into the binary one circuit will cause outputspots 16 and 3i) to be illuminated. A sixth pulse Would cause outputspot 16 to be rie-energized and output spots 23 and 3i) to beilluminated. Therentry of a seventh pulse would bring about theillumination of output spots 16, 23 and 311.

The entry of an eight light pulse causes output spots 16, Z3 and 3i) tobe de-energized and output spot 37, which represents 8, to be energizedin the following manner. The appearance of the eighth light pulse in thebinary one circuit energizes photoconductors 15 and 18 simultaneously toilluminate carry spot 19, which activates photoconductcr 17 to quenchspot 16. Carry spot 1@ also brings about the simultaneous activation ofphotoconductors 22 and 24 to illuminate spot 25'. The radiant energyfrom spot 25 then activates photoconductor 27 to quench spot 23. Theradiant energy from carry spot 25 also brings about the simultaneousactivation of photoconductors 29 and 31 for the purpose of illuminatingcarry spot 32. The radiant energy from carry spot 32, in turn, activatesphotoconductor 341, thereby bringing about the de-energization of outputspot 3i). At the same time, the radiant energy transferred by carry spot32 to photoconductor 35 illuminates output spot $7, which represents avalue of 8 in the counter.

It may thus be clearly seen that the counter, according to thisinvention, may serve to count to any magnitude in the binary notation bythe addition of other electro-optical circuits beyond the binary eightposition. To reset the counter at the end of a selected sequence ofentries, it is only necessary to open `switch 12, thereby cutting offthe input photoconductors and the locking photoconductors associatedwith each carry spot from portier source 11.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will b-e understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in theart, without departing from the spirit of the invention. 1t is theintention, therefore, to be limi-ted only as indicated by the scope ofthe following claim.

I claim:

A two-stage, cyclical-ly operable electro-optical device adapted to haveoperating voltage applied thereto, and elements each adapted to becomeand remain illuminated comprising first and second solid stateelectro-luminescent only when the voltage across the element exceeds apredetermined value, dirs-t and second circuits adapted to control thevoltages across said elements and comprised, respectively, of lrstf andvsecond solid state photoconductors which are. electrically coupled tosaid second and rstelements, respectively, and which are opticallycoupled to saidy first and second elements, respectively, to receivelight therefrom, at least said second photoconductor being electricallyin parallel with the. element to which the photoconductor iselectrically coupled, and means adapted by at least applying successiveinput signals to said circuits to render` said circuits effective toproduce oper-ation cycles for said device which are repetitive for everysuccessive group of two successive signals, and in which, in any onecycle, said rst element References; Cited by the lbiamulnexfl UNITEDsrATEs PATENTS 12/55 Allen et al. 25,0--209r X 111/59- Kazan 25o- 72:13A

RALPH (l.V NILSQN, Primary Examiner. RICHARD WQOD, MAX L. LEVY,Eqicaminers.

